1. Field of the Invention
The present invention relates to an optical tomographic imaging apparatus for use in an ophthalmologic medical care and the like.
2. Description of the Related Art
Currently, various ophthalmologic apparatuses using optical apparatuses are known. For example, various apparatuses such as an anterior eye portion imaging apparatus, a fundus camera, and a confocal scanning laser ophthalmoscope (SLO) are used as optical apparatuses for observing a subject's eye (an eye to be examined). Among them, an optical tomographic imaging apparatus based on optical coherence tomography (OCT) utilizing multi-wavelength lightwave interference is an apparatus that can acquire a tomographic image of a sample at a high resolution, and is becoming an apparatus essential for clinics specialized in retinas as an ophthalmologic apparatus. Hereinafter, this apparatus will be referred to as an OCT apparatus.
The OCT apparatus emits measurement light, which is low-coherent light, to the sample (subject's eye or part thereof), and can measure backscattering light from this sample at a high sensitivity by using an interference system or an interference optical system. The low-coherent light is characterized in that a tomographic image can be acquired at a high resolution by increasing a wavelength width thereof. Further, the OCT apparatus can acquire a tomographic image at a high resolution by scanning the measurement light on the sample. Therefore, the OCT apparatus can acquire a tomographic image of a retina on a fundus of a subject's eye, and is widely used for ophthalmologic examination or diagnosis of a retina or the like.
Generally, the OCT apparatus as an ophthalmologic apparatus is provided with a fundus observation optical system, an anterior eye observation optical system, and the like for an alignment adjustment between the apparatus and the subject's eye. The OCT apparatus is constructed by using light beams having different wavelengths in the respective optical systems and separating the wavelengths with use of a wavelength separation unit such as a dichroic mirror, to allow the OCT apparatus to be used together with these optical systems.
Now, suppose that a light source for OCT emits light having a central wavelength of 855 nm, and a wavelength band from approximately 805 nm to approximately 905 nm with a wavelength bandwidth of approximately 100 nm. On the other hand, a light source for OCT discussed in Japanese Patent Application Laid-Open No. 2011-11052 emits light having a central wavelength of 840 nm, and a wavelength band from approximately 815 nm to approximately 865 nm with a wavelength bandwidth of approximately 50 nm. Further, suppose that a light source configured to produce light having a wavelength of 780 nm is used as a light source of an SLO. In this case, an interval between the wavelength of the light source of the SLO and an end of the wavelength band of the light source for OCT is approximately 35 nm (815 nm-780 nm) in the technique discussed in Japanese Patent Application Laid-Open No. 2011-11052. On the other hand, in the case where the wavelength bandwidth is approximately 100 nm, this interval is approximately 25 nm (805 nm-780 nm). In this manner, in the case of the wavelength bandwidth of approximately 100 nm, the wavelength bandwidth of the light source for OCT is wider than that of the technique discussed in Japanese Patent Application Laid-Open No. 2011-11052, thereby leading to a reduction in the interval between the wavelength of the light source of the SLO and the end of the wavelength band of the light source for OCT.